The object of this research program is to investigate the neural processing mechanisms in the visual cortex that are relevant to the perception of positions and movements of objects in three-dimensional space. These studies are conducted by exploring in alert, visually active monkeys the response properties of cortical neurons to stereoscopically viewed pattern. During the coming year we propose to pursue two main investigations: (a) A search for the neural mechanisms underlying "global" stereopsis in cortical visual areas 17 and 18, using dynamic random-dot stereograms. (b) An analysis of the neural substrate for the stereoscopic perception of motion-in-depth in extrastriate areas of the cortex, in particular in the cortex of the posterior bank of the superior temporal sulcus (STS) known to be characterized by motion sensitive neurons.